A brushless motor described in Japanese Unexamined Patent Application Publication No. 2001-298982 is known as an example of brushless electric machines utilizing permanent magnets and electromagnetic coils.
FIG. 21 is a conceptual view showing a structural example of a related art brushless motor. This brushless motor includes an electromagnetic coil array 12 and a magnet array 32. A magnetic field is exemplified near the magnet array 32. The related art brushless motor has a problem in that the efficiency of using the magnetic field of the electromagnetic coil array 12 is considerably low because of an open magnetic field of the permanent magnets. This problem is involved not in only motors but also in generators, and is generally common to brushless electric machines.